A recent significant advancement in the field of post mixed combustion is the aspirator burner and method described and claimed in U.S. Pat. No. 4,378,205 Anderson and U.S. Pat. No. 4,541,796-Anderson. This technology enables one to carry out combustion with oxygen or oxygen-enriched air without the very high temperatures and poor mixing characteristics of oxygen combustion, thus combustion without the generation of high levels of nitrogen oxides (NO.sub.x) and without causing local hot spots within the combustion zone. This is accomplished using a defined large distance between the fuel and oxidant injection points and aspiration of furnace gases into the oxidant prior to mixture and combustion with the fuel.
Many fuels contain bound nitrogen. In the combustion of such fuels, nitrogen, which can lead to NO.sub.x formation, may come from sources exogenous to the fuel but mostly comes from the fuel itself. Accordingly methods designed to combust fuel for low NO.sub.x formation wherein nitrogen is present apart from the fuel, are generally not effective for the combustion of fuel containing bound nitrogen in order to achieve reduced NO.sub.x emissions.
In addition, known low NO.sub.x combustion Methods which relay on angled oxidant and fuel streams experience unstable combustion or blow-off if the divergence exceeds even a small angle.
It is therefore an object of this invention to provide a method for combusting fuel containing bound nitrogen to achieve reduced NO.sub.x emissions.